Invoking Interfacial Engineering Boosts Structural Stability Empowering Exceptional Cyclability of Ni-Rich Cathode.

The cycling stability of LiNi0.8Co0.1Mn0.1O2 under high voltages is hindered by the occurrence of hybrid anion- and cation-redox processes, leading to oxygen escape and uncontrolled phase collapse. In this study, an interfacial engineering strategy involving a straightforward mechanical ball milling and low-temperature calcination, employing a Se-doped and FeSe2&Fe2O3-modified approach is proposed to design a stable Ni-rich cathode. Se2- are selectively adsorbed within oxygen vacancies to form O─TM─Se bond, effectively stabilizing lattice oxygen, and preventing structural distortion. Simultaneously, the Se-NCM811//FeSe2//Fe2O3 self-assembled electric field is activated, improving interfacial charge transfer and coupling. Furthermore, FeSe2 accelerates Li+ diffusion and reacts with oxygen to form Fe2O3 and SeO2. The Fe2O3 coating mitigates hydrofluoric acid erosion and acts as an electrostatic shield layer, limiting the outward migration of oxygen anions. Impressively, the modified materials exhibit significantly improved electrochemical performance, with a capacity retention of 79.7% after 500 cycles at 1C under 4.5 V. Furthermore, it provides an extraordinary capacity retention of 94.6% in 3-4.25 V after 550 cycles in pouch-type full battery. This dual-modification approach demonstrates its feasibility and opens new perspective for the development of stable lithium-ion batteries operating at high voltages.

Revealing Lithium Nitrate-Mediated Solid-Electrolyte Interphase of Lithium Metal Anode via Cryogenic Transmission Electron Microscopy.

The cycle stability of lithium metal anode (LMA) largely depends on solid-electrolyte interphase (SEI). Electrolyte engineering is a common strategy to adjust SEI properties, yet understanding its impact is challenging due to limited knowledge on ultrafine SEI structures. Herein, using cryogenic transmission electron microscopy, we reveal the atomic-level SEI structure of LMA in ether-based electrolytes, focusing on the role of LiNO3 additives in SEI modulation at different temperature (25 and 50 °C). Poor cycle stability of LMA in the baseline electrolyte without LiNO3 additives stems from the Li2CO3-rich mosaic-type SEI. Increased LiNO3 content and elevated operating temperature enhance cyclic performance by forming bilayer or multilayer SEI structures via preferential LiNO3 decomposition, but may thicken the SEI, leading to reduced initial Coulombic efficiency and increased overpotential. The optimal SEI features a multilayer structure with Li2O-rich inner layer and closely packed grains in the outer layer, minimizing electrolyte decomposition or corrosion.

Local Isomeric Polar Nanoclusters Enabled Superior Capacitive Energy Storage Under Moderate Fields in NaNbO3-Based Lead-Free Ceramics.

The high-field energy-storage performance of dielectric capacitors has been significantly improved in recent years, yet the high voltage risks of device failure and large cost of insulation technology increase the demand for high-performance dielectric capacitors at finite electric fields. Herein, a unique superparaelectric state filled with polar nanoclusters with various local symmetries for lead-free relaxor ferroelectric capacitors is subtly designed through a simple chemical modification method, successfully realizing a collaborative improvement of polarization hysteresis, maximum polarization, and polarization saturation at moderate electric fields of 20-30 kV mm-1. Therefore, a giant recoverable energy density of ≈5.0 J cm-3 and a high efficiency of ≈82.1% are simultaneously achieved at 30 kV mm-1 in (0.9-x)NaNbO3-0.1BaTiO3-xBiFeO3 lead-free ceramics, showing a breakthrough progress in moderate-field comprehensive energy-storage performances. Moreover, superior charge-discharge performances of high-power density ≈182 MW cm-3, high discharge energy density ≈4.3 J cm-3 and ultra-short discharge time <70 ns as well as excellent temperature stability demonstrate great application potentials for dielectric energy-storage capacitors in pulsed power devices. This work provides an effective and paradigmatic strategy for developing novel lead-free dielectrics with high energy-storage performance under finite electric fields.

Defect Engineering of 2D Copper Tin Composite Nanosheets Realizing Promoted Electrosynthesis Performance of Hydrogen Peroxide.

The transformation of the two-electron oxygen reduction reaction (2e-ORR) to produce hydrogen peroxide (H2 O2 ) is a promising green synthesis approach that can replace the high-energy consumption anthraquinone process. However, designing and fabricating low-cost, non-precious metal electrocatalysts for 2e-ORR remains a challenge. In this study, a method of combining complexation precipitation and thermal treatment to synthesize 2D copper-tin composite nanosheets to serve as the 2e-ORR electrocatalysts is utilized, achieving a high H2 O2 selectivity of 92.8% in 0.1 m KOH, and a bulk H2 O2 electrosynthesis yield of 1436 mmol·gcat -1 ·h-1 using a flow cell device. Remarkably, the H2 O2 selectivity of this catalyst decreases by only 0.5% after 10,000 cyclic voltammetry (CV) cycles. In addition, it demonstrates that the same catalyst can achieve 97% removal of the organic pollutant methyl blue in an aqueous system solution within 1 h using the on-site degradation technology. A reasonable control of defect concentration on the 2D copper-tin composite nanosheets that can effectively improve the electrocatalytic performance is found. Density functional theory calculations confirm that the surface of the 2D copper-tin composite nanosheets is conducive to the adsorption of the key intermediate OOH* , highlighting its excellent electrocatalytic performance for ORR with high H2 O2 selectivity.

Differing Electrolyte Implication on Anion and Cation Intercalation into Graphite.

Emerging dual-graphite batteries (DGBs) capture extensive interest for their high output voltage and exceptional cost-effectiveness. Yet, developing electrolytes compatible with both the cathode and anode stands to be a tremendous challenge, and how electrolyte impacts anion and cation intercalation into graphite remains inexplicit or controversial. Herein, we have evaluated the performance of graphite anode and cathode in typical ethyl methyl carbonate (EMC) based electrolytes and unveiled their electrode-electrolyte interphase using Cryogenic transmission electron microscopy (Cryo-TEM). The addition of fluoroethylene carbonate (FEC) brings substantial improvement in cycle stability and Coulombic efficiency for both the graphite cathode and anode, but its implication on cation and anion intercalation differs. FEC is involved in anodic side reactions to produce a LiF-embedded solid-electrolyte interphase layer. It is much thinner and more uniform than that formed in the electrolyte without FEC, which is correlated with less graphite exfoliation and enhanced stability. As for the graphite cathode, both basal and edge planes are largely bare, and only few scattered byproducts are found. In addition, we also reveal layer bending and local lattice disordering of the graphite cathode based on multiple Cryo-TEM images, which are speculated to be caused by high lattice strain induced by anion intercalation and local oxidation under high voltage. The absence of cathode-electrolyte interphase (CEI) layers overturns the paradigm of attributing cathodic performance to CEI features and is regarded as a fundamental reason for severe self-discharge of graphite cathode. FEC helps to alleviate graphite exfoliation issues and enhance cycle stability, and we ascribe it to weakened solvation, which means reduced probability of solvent co-intercalation during charging, rather than compositional changes of cathodic byproducts.

Borate-Based Artificial Solid-Electrolyte Interphase Enabling Stable Lithium Metal Anodes.

Lithium (Li) metal is considered as the "holy grail" of anode materials for next-generation high energy batteries. However, notorious dendrite growth and interfacial instability could induce irreversible capacity loss and safety issues, limiting the practical application of Li metal anodes. Herein, we develop a novel approach to construct a borate-based artificial solid-electrolyte interphase (designated as B-SEI) through the reaction of metallic Li with triethylamine borane (TEAB). According to our cryogenic electron microscopy (Cryo-EM) characterization results, the artificial SEI adopts a glass-crystal bilayer structure, which facilitates uniform Li-ion transport and inhibits dendrite growth during Li plating. Benefiting from such an artificial SEI, the Li anode delivers an improved rate performance and prolonged cycle life. The symmetric Li/B-SEI||Li/B-SEI cell can maintain stable cycling for 700 h at a high current density of 3 mA cm-2. The full-cell pairing Li/B-SEI with LiFePO4 only exhibits minimal capacity decay after 500 cycles in a conventional carbonate-based electrolyte. This work demonstrates the feasibility of building a boride-based artificial SEI to stabilize the Li metal anode based on microscopic characterization results and comprehensive electrochemical data, which represents a promising avenue to develop practical Li metal batteries.

Revealing Structural Insights of Solid Electrolyte Interphase in High-Concentrated Non-Flammable Electrolyte for Li Metal Batteries by Cryo-TEM.

High-concentrated non-flammable electrolytes (HCNFE) in lithium metal batteries prevent thermal runaway accidents, but the microstructure of their solid electrolyte interphase (SEI) remains largely unexplored, due to the lack of direct imaging tools. Herein, cryo-HRTEM is applied to directly visualize the native state of SEI at the atomic scale. In HCNFE, SEI has a uniform laminated crystalline-amorphous structure that can prevent further reaction between the electrolyte and lithium. The inorganic SEI component, Li2 S2 O7 , is precisely identified by cryo-HRTEM. Density functional theory (DFT) calculations demonstrate that the final Li2 S2 O7 phase has suitable natural transmission channels for Li-ion diffusion and excellent ionic conductivity of 1.2 × 10-5 S cm-1 .

Cu-Doped Iron Oxide for the Efficient Electrocatalytic Nitrate Reduction Reaction.

The electrochemical nitrate reduction reaction (NO3RR) is a promising alternative synthetic route for sustainable ammonia (NH3) production, because it not only eliminates nitrate (NO3-) from water but also produces NH3 under mild operating conditions. However, owing to the complicated eight-electron reaction and the competition from the hydrogen evolution reaction, developing catalysts with high activities and Faradaic efficiencies (FEs) is highly imperative to improve the reaction performance. In this study, Cu-doped Fe3O4 flakes are fabricated and demonstrated to be excellent catalysts for electrochemical conversion of NO3- to NH3, with a maximum FE of ∼100% and an NH3 yield of 179.55 ± 16.37 mg h-1 mgcat-1 at -0.6 V vs RHE. Theoretical calculations reveal that doping the catalyst surface with Cu results in a more thermodynamically facile reaction. These results highlight the feasibility of promoting the NO3RR activity using heteroatom doping strategies.

Bismuth Ferrite as an Electrocatalyst for the Electrochemical Nitrate Reduction.

Electrochemical nitrate reduction has become an appealing "waste-to-wealth" approach for sustainable NH3 synthesis owing to its mild operating conditions. However, developing catalysts with high activities and Faradaic efficiencies for this complicated eight-electron reaction is a great challenge. Herein, bismuth ferrite (BiFeO3) flakes, with a distorted perovskite-type structure, are demonstrated to be excellent catalysts for electrochemical NH3 synthesis via nitrate reduction, with a maximum Faradaic efficiency of 96.85%, NH3 yield of 90.45 mg h-1 mgcat-1, at -0.6 V vs. reversible hydrogen electrode. During the nitrate reduction reaction, the crystalline BiFeO3 rapidly converts into an amorphous phase, which is stable in the long term reaction. These results open a new window for rational design of more active and durable electrocatalysts.